The ACLU report, called "Beyond Zero Tolerance: Discipline and Policing in Pennsylvania's Public Schools," points to high rates of suspensions and disparities in how black and Latino students and students with disabilities were treated.

"Part of the problem is that under zero tolerance, a wide range of behaviors, from dress code violations to talking back, are now being punished as disorderly conduct, disruption and defiant behavior," the report's author, Harold Jordan, said.

The report found that, in 2011-12, school districts issued more than 166,000 out-of-school suspensions, or 10 suspensions per 100 students. In addition, 1,808 students were expelled from school, and police arrested 5,261.

While black students account for 13.6 percent of Pennsylvania's students, they made up nearly half of the out-of-school suspensions. One of 10 Latino students was suspended at least once, which the ACLU said is one of the highest Latino suspension rates in the nation.